Excellent banger at Christmas dinner, standard (11)
I believe the answer is:
crackerjack
'excellent' is the definition.
(thesaurus)
'banger at christmas dinner standard' is the wordplay.
I cannot really see how this works, but
'banger' could be 'cracker' (synonyms) and 'cracker' is present in the answer.
'standard' could be 'jack' (both can refer to a flag) and 'jack' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for crackerjack that I've seen before include "Exceptionally good" , "Wonderful (person or thing)" , "Excellent (person or thing)" , "Exceptional (thing or person) - 1970s' children's programme" .)